Piston



Sept. 1, 1936. A L NELSQN PISTON Original Filed Dec. 16, 192'? 2 Sheets-Sheet l Sept. 1, 1936. A, 1 NELSON PISTON Original Filed Deo. 16, 1927 2 Sheets-Sheet 2 Patented Sept. 1, 1936 PATENT OFFICE PISTON Adolph L. Nelson, Detroit, Mich., assig'nor to BohnAluminum & Brass Corporation, Detroit,

Mich.

Application December 16, 1927, serial No. 240,379

o. Renewed March 27, 1935 16 Claims. (Cl. 309-13) This invention relates toupistons, particularly to pistons for use in internal combustion engines,

and aims to improve the construction of such pistons. y Y

The invention is especially applicable to light weight pistons forl automobile engines, and has fo; anvobject to provide novel means for carrying thrustloads from the piston pinto the cylinderbearing portions of the piston. 'The piston comprises a head having piersextending downwardly to which the skirt is attached, and a particular,

feature is an offset arrangement of the lower end of the piers where they join the skirt.

A further feature of invention resides in providing a construction in-which the-upper end of the skirt isgiven a certain amount of exibility to enable it to ride-smoothly over any tight places in the cylinder even when lthe piston clearance is very small.-

The parts are so arranged that it is unnecessary to have any. slots extending upwardly into the skirt, and the lower end of the skirt forms a continuous annulus. A

The invention also provides a pistonin which the lower end ofthe skirt is provided with a piston ring and which can be molded in a permanent mold having a three piece core.

While preferred embodiments of the invention have been disclosed for purposes of illustration, it should be understood that various changes can be made in the structure without departing from the spirit and scope of the invention as hereinafter set forth and claimed.

In the drawings:

Fig. 1 is a side elevation of a piston.

Fig. 2 is anelevation partly in section taken at right angles to Fig. l. Y

Fig. 3 is an elevation showing a variation.

Fig. 4 is an elevation showing a further variation.

Fig. 5 is a side elevation of a piston embodying an additional feature.

Fig. 6 is a bottom plan view of a piston.

Fig. 7 is an elevation partly in section of a piston having a ring at its lower end.

Fig. 8 is a section on lines 8-8 of Fig. '7 but with the ring removed and with the core sections in place to illustrate the method of casting.

Referring to the drawings for a more particular description of the invention, the reference numeral I0 indicates the head of the piston, while numerals II are applied to piers depending from the head and having piston pin bosses I2 formed therein. The skirt comprises an annular portion I3 which has a homogeneous connection with the lower ends of the piers, and cylinder-bearing slippers I4 and I5 which project upwardly l from the 'annulus I3, the slippers being separated from the head by slots I 6 and from the piers by vertical openings I1. f 5

The head and skirt are formed of any suitable material,.such as a light-weight alloy, and in order to control the expansion of the upper ends of the slippers .a pair of struts I8 maybe placed across the piston connecting .the slippers, 10 the struts being formed of some material less expansible than the piston material. lThese struts prevent excessive expansion of the upper end of the skirt, and in connection therewith it is necessaryto form the vpiston in such a manner that the lower end of the skirt-will. not expand into harmful contact with the walls of the cylinder in which the piston is operating.

This result may be attainedin a variety of ways. For example, in Figs. 1 and 2 I have shown 20 that the skirt may be formed on a slight taper, with the diameter of the lower end of the skirt at A-A slightly less than the diameter at the upper end of the skirt, at B-B.

Alternately or additionally the lower end of the skirt may be constructed in such a manner that the diameter C-C parallel to the axis of the pin bosses is less than the diameter D-D, perpendicular to said axis. A convenient method of producing this construction is to grind the lower end of the skirt to an oval or other suitable shape while finish grinding the piston.

Either of the arrangements just described provides the annulus I3 with extra clearance below the pin bosses, so that this part of the skirt may expand to a reasonable extent without producing excessive friction in the cylinder.

A particular feature of the invention resides in the way in which the annulus I3 is connected with the lower ends of the piers II. As shown in Fig. 1 these connections I9 are offset from the center line of the pier, and extend up along the sides of the slipper I4 for a considerable distance. This offset arrangement has several advantageous features. For example, in this construction the upper part of the connection I9 approaches the line of thrust from the piston pin to the slipper Ill, and by inserting the piston in the cylinder so that the slipper I4 will carry the main thrust load, the connection I9 will 50 help to carry the thrust load and thereby lighten the load on the strut joints. By extending the connection I9 high enough along the slipper I4 it is possible to omit the anchorage at thc center of the strut.

part of the skirt a certain amount of flexibility,

and this' may be done by cutting a lslot or slots downwardly into the skirt as shown at 22 in Fig. l 5. This construction permits tting the upper end of the skirt with an unusually small clearance in the cylinder, as the struts control the thermal expansion while the slots permit slight yielding to allow the piston to run by a tight spot in the cylinder without undue friction. This arrangement for making the upper end of the skirt ilexible may be used with any typeoi pier construction, and even without the struts, since the combination of the iiexible upper skirt end with solid lower end may be used to produce a piston without struts that will operate satisfactorily.

VAnother feature of the invention resides in making provision for a piston ring at the lower end of the skirt while using a permanent mold having a three-piece core.- The Wall'of the skirt must be keptV as thin as possible, and to form aring groove in thewall necessitates forming a rib on theinside of the skirt to bridge over'the".

groove. `But.with.aV threepiece corevit is'impossible to 'cast ribs in the--Wall of the skirt abutting the ends of `the middle-'core piece 234V since'this latter Apiece must-be pulled straight` out in order; to permit collapsing the'side cores 24 toward the center to clear the projecting parts of the wall. The ribs 25 are therefore cast'only on the skirt portions facing the core pieces 24, and the `ring groove'26 extends into 'the rib 25 and cuts completely through the skirt wall at the points 21 lying between the ends of the ribs 25. A piston ring 28 isaccommodated in the ring groove 2S.

I claim:

l. A piston comprising a head, piersdepending from the head and having pin bosses formed therein, an annular portion Aconnected to the lower ends of the piers, tongues Vextending upwardly from the annular portion and formed of light weight 'materiaL and struts of relatively inexpansible material extending across the piston between the tongues, the line of connection between each pier and the annular portion extending partway up along the side of a tongue.

2. A piston comprising a head and a skirt formed of light Weight material, struts of relatively inexpansible material controlling the expansion of the upper end of the skirt, the skirt being tapered to give the lower end of the skirt a smaller diameter than the upper end thereof when cold.

3. A piston comprising a head, piers depending from the head and having pin bosses formed therein, a skirt having an uninterrupted annular portion connected to the lower ends of the piers and tongues extending upwardly from the annular portion, the skirt being tapered to give the lower end of the skirt a smaller diameter than the upper end thereof when cold.

4. A piston comprising a head, piers depending from the head and having pin bosses formed therein, a skirt'formed of light weight material having an annular portion connected to the lower ends of the piers and tongues extending upwardly from the annular portion, strut-s of relatively inexpansible material controlling the expanslon of the upper end of the skirt, the skirt being tapered to give the lower end of the skirt asmaller diameter than the upper end thereof when cold.

5. A piston comprising a head, piers depending from the headand having pin -bosses lformed therein, a skirtjormed of` lightweight material having an uninterruptedan'nular' portion connected to the lower ends of the piers and tongues extending upwardly from the annular portion, struts of relatively inexpansible material controlling the expansion Yof the upper end of the fskirt, the skirtbein'g-"tapered to give the lower end of the skirt a. smaller diameter than the upper end thereof when cold.

6. A piston' comprising a head, piers depending from the f head and having pin bosses formed therein, a skirt including bearing portions separated at their upper ends from the head, parts connecting thelower' ends'of 'the bearing portions to each other, thehead and'bearing portions being-formed of a relatively lightweight material, a pair of struts extending between the` bearing portions, the struts beingrformed-of a. material having Va lower coefcient o f thermal expansion than the material of the bearing-portionsiapair of webs, each web being homogeneous with-a' pier and with a bearing portion,the webs-extending in a general directionoutwardlyfand dowhwardlyl tions to each other, the head and bearng'por- 1 tions being v-forrnedbf Varelatively light weight material, a pair of struts extending between'the bearing portions,"the"struts 'being formed fof a material having a'lower coeiiicient of thermal ex-v panslon than the material of the bearing portions,

a pair of webs, each web being homogeneousV with a pier and with a' bearing portion, the webs extending in a generaldirection. outwardly and downwardly from the pinibosses, the bearingportion adjacent the webs being formed with a slot extending upwardly fromthe lower edge of the skirt.

8. A piston comprising la, head, piers depending from the head and having pin bosses formed therein, a skirt including bearing portions separated at their upper ends from the head, parts connecting the lower ends of the bearing portions to each other, the head and bearing portions being formed of a relatively light weight material, a pair of struts extending between 'the bearing' portions, the struts being formed of a material having a lower coeiiicient of thermal expansion than the material of the bearing portions, a pair of webs, each web being homogeneous with a pier and with a bearing portion, the webs extending in a general direction outwardly and downwardly from the pin bosses, the bearing portion farthest away from the oiset webs be- .ing formed with a slot extending upwardly from the lower edge of the skirt.

9. A piston comprising a head, a skirt having pin bosses formed therein, an arcuate rib formed on the inside of the skirt below the piston pin opening in each pin boss, each of said ribs extending circumferentially over a considerable arc of the wall of the skirt, the ribs being discontinued over small arcs at points spaced 90 from the pin bosses, the skirt being formed with a groove extending into said ribs and cutting completely through the skirt along the arcs wherethe ribs are discontinued` 10. A piston comprising a head, a skirt having pin bosses formed therein, an arcuate rib formed on the inside of the skirt below the piston pin opening in each pin boss, each of said ribs extending circumferentially along the skirt wall for at least of the circumference of the skirt. the ribs being discontinued over small arcs on opposite sides of the skirt at points midway between the pin bosses, the skirt being formed with a piston-ring groove extending into said ribs and cutting completely through the skirt along the arcs where the ribs are discontinued.

11. A piston comprising a head. a skirt` having pin bosses formed therein, two thrust faces between the pin bosses, the thrust faces lying on opposite sides of the skirt and extending from the top of the skirt to the bottom of the skirt. an arcuate rib formed on the inside of the skirt below the piston pin 'opening in each pin boss and extending circumferentially along the skirt wall from one thrust face to the other, the ribs being discontinued over small arcs at the circumferential center of each thrust face. the skir-t being formed with a groove extending into said ribs and cutting completely through the skirt along the arcs where the ribs are discontinued.

12. A piston comprising a head, piers depending from the head and having pin bosses formed therein, a skirt including bearing portions separated at their vupper ends from the head. the head and bearing portions being formed of a relatively light weight material, a. pair of struts extending chordally of the piston between the bearing portions, the struts being formed of a material having a lower coeiiicient of thermal expansion than the material of the bearing portions, each strut having its opposite ends in contact with opposite bearing portions, a pair of webs, each web being homogeneous with a pier and with a bearing portion, the webs extending in general direction outwardly and downwardly from the pin bosses.

13. A piston comprising a head, a skirt having pin bosses formed therein, arcuate ribs formed on the inside of the skirt, each of said ribs extending circumferentially along the skirt wall for at least 90 of the circumference of the skirt, the ribs being discontinued over small arcs on opposite sides of the skirt at points midway between the pin bosses, the skirt being formed with a pistonring groove extending into said ribs and cutting completely through the skirt along the arcs where the ribs are discontinued.

14. A piston comprising a head, a skirt having piston pin bosses formed therein, parts of the skirt wall lying adjacent the ends of a diameter at right angles to the axis of the pin bosses constituting thrust faces, tle part of the skirt wall lying below the horizontal plane ofthe axis of the piston pin bosses comprising an annular part, said annular part being formed with a piston ring groove, the piston-ring groove being dened by side walls continuous circumferentiaily of the piston, and a bottom wall continuous circumferentially around the piston except at the center of each thrust face, where the bottom wall is discontinued and the groove cuts completely through the skirt wall.

15. A piston comprising a head, a skirt having piston pin bosses formed therein, part of the skirt lying below the axis of the piston pin bosses beingl formed with a piston-ring groove, parts of the skirt projecting inwardly around the groove to form a bottom wall for the groove continuous except at two places adjacent the ends of a diameter perpendicular to the axis of the piston pin bosses, and at said two places there are no parts projecting inwardly from the skirt wall.

16. A piston comprising a head, a skirt having piston pin bosses formed therein, parts of the circumferential wall of the skirt lying between the Vbosses on each side of the skirt constituting thrust faces, the skirt being formed with a pistonring groove, parts of the skirt projecting inwardly around the groove to form a bottom wall for the groove. the bottom wall being circumferentially continuous except adiacent the center of each thrust face, where the groove cuts completely through the skirt wall, the center of each thrust face from' points adjacent the upper end of the skirt and extending down to the bottom of the skirt, being free of any inwardly projecting parts.

ADOLPH L. NELSON.

DISCLAIMER 2,052,985.Ad0lph L. Nelson, Detroit, Mich. PIsToNs. Patent dated September 1, 1936. Disclaimer led December 29, 1939, by the assignee, Bohn Aluminum d Brass Corporation.

I'Iercby enters this disclaimer t claims 9, 10, 11, 13, 14, 15, and 16 of said pinten t..

[Qcal Gazette January 23, 1940.] 

